MEMS (Microelectromechanical Systems) include mechanical and electrical components having dimensions in the order of microns or smaller. MEMS structures can be employed in numerous applications including switches, actuators, valves and sensors. Microelectromechanical switches for radio frequency (RF) applications have been recognized as an enabling technology because the signal via the switches remains linear over a much broader bandwidth than similarly targeted solid state devices.
Electrical switches make and break electrical connection, and involve a switching electrical contact system that must then be actuated in some way. Switches can often be described as, for example, bi-stable latching, non-latching, and so on, depending on whether the switch remain closed after actuation forces are removed (latching) or not (non-latching). When switches are not bi-stable, they can be classified as “normally-open” or “normally-closed.”
Majority of prior art electrostatically actuated switch, for example, employs a cantilever arm to make or break a switch contact. The switch contact may be electrostatically pulled down by a “gate” electrode so that a metalized contact material on the end of the cantilever makes contact with a metalized contact pad, thereby closing the circuit. The switch may include multiple layers that can result in residual stresses within the cantilever arm. Such configuration can cause warping of members that can destroy functionality, large actuation voltages, and durability issues associated with stiction and hot-switching. Additionally, such cantilever type switches are not readily modified to a latching configuration.
Another prior art MEMS electrostatic switch involves the use of a metallic membrane to close the switch contact(s). The switch is generally open and the membrane is closed by a pulling force that may be generated through an electrostatic field created between the membrane and a “gate” electrode. Consequently, such prior art switch suffer from stiction, plastic deformation and residual stresses that reduce life and production yields.
Based on the foregoing it is believed that a need exists for an improved electrostatically actuated RF-MEMS switch that exhibits fast switching, low insertion loss, high bandwidth and low voltage actuation operation, as described in greater detail herein.